Impact of cryopreservation on bull () semen proteome

Cryopreservation of bull spermatozoa is a well-established technique, allowing artificial insemination of cattle on a commercial scale. However, the extent of proteome changes in seminal plasma and spermatozoa during cryopreservation are not yet fully known. The objective of this study was to compare the proteomes of fresh, equilibrated, and cryopreserved bull semen (spermatozoa and seminal plasma) to establish the changes in semen proteins during the cryopreservation process. Semen was collected from 6 mature Holstein Friesian bulls. After sample processing, comparative analysis and identification of proteins was performed using 2-dimensional difference in-gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry. Analysis of spermatozoa extracts revealed that 25 identified protein spots, representing 16 proteins, underwent significant ( < 0.05) changes in abundance due to equilibration and cryopreservation. Eighteen protein spots decreased in abundance, 5 protein spots increased in abundance, and 2 protein spots showed different, specific patterns of abundance changes. Analysis of seminal fluid containing seminal plasma showed that 6 identified protein spots, representing 4 proteins, underwent significant ( < 0.05) changes in abundance due to equilibration and cryopreservation. Two protein spots increased in abundance and 4 decreased in abundance. Semen extending and equilibration seems to be responsible for a significant portion of the proteome changes related to cryopreservation technology. Most sperm proteins affected by equilibration and cryopreservation are membrane bound, and loss of those proteins may reduce natural spermatozoa coating. Further research is needed to unravel the mechanisms of the particular protein changes described in this study and establish the relationship between those changes and sperm quality.

Potassium ions in extender differentially influence the post-thaw sperm motility of salmonid fish

Potassium ions are known to have an inhibitory effect on the sperm motility of salmonids. For this reason, the addition of K(+) to the extender is frequently applied. However, the effect of the addition of K(+) to the extender has not yet been tested. The aim of this study was to test the influence of potassium ion supplementation of the extender on the sperm motility parameters from five Salmonidae species (rainbow trout (Oncorhynchus mykiss), sex-reversed female rainbow trout, whitefish (Coregonus lavaretus), brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis)). Semen samples were diluted in extender containing 0.18 M glucose in 9% methanol (GM) supplemented with 0, 20 or 40 mM potassium chloride. After thawing sperm were stored for 30, 60, 120 and 240 min at 4 °C. Our results demonstrated that the presence of potassium ions in the extender had a negative effect on percentage of motile sperm in four of the salmonid species. In contrast, potassium ions appeared to have a positive effect on percentage of post-thaw motile sperm in whitefish semen. However, this effect could be mimicked by changing the osmolality of the extender (which was achieved by increasing the glucose concentration to 0.22 M). The addition of potassium ions turned out to have no positive effect on post-thaw storage time. Our results suggest that osmolality, rather than potassium ions, seems to be essential for cryopreservation success of salmonids sperm. Further studies should focus on the effects of small changes in osmolality on the post-thaw quality of semen.

Motility of carp spermatozoa is associated with profound changes in the sperm proteome

In freshwater cyprinids, spermatozoa are quiescent in seminal plasma and sperm motility is initiated by a decrease in osmolality (hypo-osmotic shock) after discharge into the aqueous environment. However, it is unknown at present if and to what extent changes in proteins are involved in carp sperm motility. Therefore, the aim of our study was to identify proteins related to carp sperm motility through a comparison of immobilized and activated carp spermatozoa using a 2D-DIGE approach. Our results, for the first time indicated that carp sperm motility is associated with changes in protein content. Seventy-two differentially expressed proteins were identified. These proteins are mainly involved in ubiquitin-proteasome pathways, glycolysis, the TCA cycle, remodeling and are putatively related to sperm energy metabolism and motility. Moreover proteins associated with oxidative stress responses, signal transduction by Ca(2+)-dependent MAPK cascades, and PKC and protein folding have been identified. The proteins involved in carp sperm motility were localized to the cytoplasm, mitochondria, cytoskeleton, nucleus and sperm membrane. The identification of a high number of proteins involved in carp sperm motility would contribute to current knowledge about the molecular mechanisms of sperm motility in freshwater fish.

BIOLOGICAL SIGNIFICANCE

To the best of our knowledge, few changes in proteins involved in the initiation of fish sperm motility have been identified. This is a limited number of proteins compared with the 80 recently identified proteins involved in human sperm motility. However, no proteomic studies of sperm motility have yet been performed on freshwater fish. Our present study allowed for the first time a comprehensive characterization of the proteins associated with carp sperm motility and a better understanding of the molecular mechanisms underlying sperm motility activation and maintenance. The application of 2D-DIGE facilitated the identification proteins crucial for sperm structural organization and motility. The identification of a high number of proteins involved in carp sperm motility would contribute appreciably to the presently limited information available on the mechanisms of sperm motility in freshwater fish. Moreover the identified list of proteins will create a platform for future studies designed to assess the functional significance of specific proteins in sperm motility.

Temporal Changes in Gametogenesis of the Invasive Chinese Pond Mussel Sinanodonta woodiana (Lea, 1834) (Bivalvia: Unionidae) from the Konin Lakes System (Central Poland)

Gametogenesis and the temporal changes occurring in the ovaries and testes throughout the reproductive cycle in the invasive alien bivalve, Chinese pond mussel Sinanodonta woodiana (Lea), from the heated Konin lakes system (central Poland) were studied using histological techniques. S. woodiana was confirmed to be a gonochoristic species with overall sex ratio of 1:1. The examined morphological parameters of Chinese pond mussel spermatozoa, i.e. 42 μm mean total length; 4.3 μm mean head length and the maximum size of previtellogenic (34-43 μm) and vitellogenic oocytes (75-83 μm) are consistent with values established for closely related members of the Unionidae family. Our results suggest that S. woodiana in the Konin lakes system are able to spawn throughout March to October, with a season of higher reproductive activity in females extending from March to April. This type of reproductive biology may contribute to the Chinese pond mussel's success in thriving in freshwater ecosystems.

Expression of apolipoprotein A-I and A-II in rainbow trout reproductive tract and their possible role in antibacterial defence

Antimicrobial proteins such as apolipoproteins A (ApoA-I and ApoA-II) play an important role in the primary defence barrier in vertebrates including fish. The aims of the present study were to isolate and characterise rainbow trout seminal plasma ApoA-I and ApoA-II, to examine the mRNA expression of each apolipoprotein in testis and spermatic ducts, and to test the antibacterial properties of the apolipoproteins. Using a three-step isolation procedure consisting of ion-exchange chromatography, gel filtration and preparative SDS-PAGE, apolipoproteins were purified and identified as ApoA-I and ApoA-II. Both apolipoproteins were represented by several proteoforms. The expression of ApoA-I and ApoA-II mRNA in the reproductive tract and their antibacterial properties against Escherichia coli suggest that seminal apolipoproteins play an important role in innate immunity in the rainbow trout reproductive tract. The functions of seminal ApoA can be related to protection of sperm and reproductive tissue from microbial attack and to the maintenance of sperm membrane integrity.

Cryopreservation-induced alterations in protein composition of rainbow trout semen

The aim of this study was to detect cryopreservation-induced alterations in the protein composition of rainbow trout semen using two independent methods 1DE SDS-PAGE prefractionation combined with LC-MS/MS and 2D difference gel electrophoresis followed by MALDI-TOF/TOF identification. Here, we show the first comprehensive dataset of changes in rainbow trout semen proteome after cryopreservation, with a total of 73 identified proteins released from sperm to extracellular fluid, including mitochondrial, cytoskeletal, nuclear, and cytosolic proteins. Our study provides new information about proteins released from sperm, their relation to sperm structure and function, and changes of metabolism of sperm cells as a result of cryopreservation. The identified proteins represent potential markers of cryoinjures of sperm structures and markers of the disturbances of particular sperm metabolic pathways. Further studies will allow to decipher the precise function of the proteins altered during rainbow trout cryopreservation and are useful for the development of extensive diagnostic tests of sperm cryoinjures and for the successful improvement of sperm cryopreservation of this economically important species.

New extender for cryopreservation of Siberian sturgeon (Acipenser baerii) semen

The goal of this study was to develop a simple glucose-methanol extender for cryopreservation of Siberian sturgeon (Acipenser baerii) semen. Semen quality was assessed by determining post-thaw sperm motility and fertilizing ability at hatching stage. We tested the effect of glucose concentration (0, 0.10, 0.15, 0.20 and 0.30 M) in a methanol extender on post-thaw sperm motility. Sperm motility parameters and fertilizing ability of semen cryopreserved in 0.1 M glucose in 15% methanol (GM) were compared to previously described Tris-sucrose-KCl in 10% - methanol extender (TSKM). Additionally, sperm motility and fertilizing ability in relation to 30 min equilibration in GM extender before cryopreservation and 30 min of post-thaw storage were determined. The beneficial effect of the glucose for semen cryopreservation was related to its concentration with a quite narrow optimum of 0.1 to -0.15 M. The fertilization rates of frozen/thawed sperm were similar for both (TSKM and GM) tested extenders. The sperm motility and fertilization rate were not affected either by 30 min equilibration in GM extender or by 30 min of post-thaw storage. Our work indicates that the use a simple extender consisting of 0.1M glucose in 15% methanol can be an alternative cryopreservation method to those previously described for sturgeons. The use of an equilibration period and the possibility of post-thaw semen storage can improve organization of hatchery work and help with logistics of large-scale hatchery operations.

Maturation of spermatozoa from rainbow trout (Oncorhynchus mykiss) sex-reversed females using artificial seminal plasma or glucose-methanol extender

Masculinized females (sex-reversed females) produce only homogametic spermatozoa (X) for fertilization which is desired for the production of all-female rainbow trout populations. The milt of sex-reversed females is of low quality and must be matured through extension in maturation solutions. The aim of this study was to compare the usefulness of glucose-methanol (GM) extender with artificial seminal plasma (ASP) extender for the maturation of milt of sex-reversed female rainbow trout. Milt suspensions were incubated at 4 °C for either 15 minutes (GM extender) or 120 minutes (ASP extender). Incubation of milt diluted in either the GM or ASP extender caused a significant (P < 0.05) increase in the percentage of sperm motility to 76.1 ± 10.9% and 74.7 ± 18.6% for GM and ASP, respectively, but no differences between both the extenders were found. Incubation also increased the average path velocity, straight line velocity, and linearity values of spermatozoa diluted with the GM extender; at the same time, none of the other parameters changed for ASP suspensions. Sperm diluted with ASP was characterized by higher curvilinear velocity and lateral head displacement values. Percentage of eyed embryos produced by fertilization using milt diluted in the GM extender amounted to 63.6 ± 16.4% and 67.2 ± 11.9% for sperm-to-egg ratio of 300,000:1 or 600,000:1, respectively and was lower (P < 0.05) compared with that of ASP extender (79.5 ± 5.8% and 80.3 ± 4.7% for sperm-to-egg ratio of 300,000:1 or 600,000:1, respectively). The results of our study clearly report that the mechanism of sperm maturation by the GM extender differs from that based on ASP.

Characterization, expression and antibacterial properties of apolipoproteins A from carp (Cyprinus carpio L.) seminal plasma

Apolipoproteins A are multifunctional proteins that, in addition to contributing to lipid metabolism and transport, are associated with the innate immune system in fish. Using a three step isolation procedure consisting of affinity chromatography on Blue-Sepharose, delipidation and reverse phase HPLC we isolated apolipoproteins from carp seminal plasma and identified them as ApoA-I and Apo-14 kDa. Moreover, we provided the full-length cDNA sequence of ApoA-I encoding 257 amino acids including a 18 amino acid signal peptide and a 4 amino acid propeptide. Apolipoproteins corresponded to the most abundant proteins in carp seminal plasma. Both ApoA-I and Apo-14 kDa were represented by several proteoforms that differ both in molecular mass and isoelectric point. The proteoforms of ApoA-I characteristic for seminal plasma were distinguished from those of blood. Carp seminal plasma ApoA-I and Apo-14 kDa showed a high immunologic similarity to their counterparts in carp blood and seminal plasma of other Cyprinid species. The mRNA expression analysis and immunohistochemical study suggest synthesis and secretion of ApoA-I and Apo-14 kDa in the fish reproductive tract and suggest a role in spermatogenesis and the stabilization of sperm membrane. Moreover, ApoA-I displayed bactericidal activity against Escherichia coli and bacteriostatic activity against Aeromonas hydrophila which suggests that ApoA-I is associated with innate immune system of the fish reproductive tract.

Protease in sturgeon sperm and the effects of protease inhibitors on sperm motility and velocity

In mammals, proteases are present in sperm acrosome and play key role in fertilization. Sturgeon sperm has an acrosome, but its physiology, biochemistry, and potential role in fertilization are unknown. In the present study, we have observed high protease activity in acidic extract of intact sperm compared to that of seminal plasma in sterlet (Acipenser ruthenus). The protease activity was decreased and increased in acidic extract of motility-activated sperm and in the activation medium, respectively. Molecular analysis revealed total protease and serine (acrosin) protease activities in sperm acidic extract which was accumulated in a protein band with relative molecular mass of 35 kDa. Immunoelectron microscopy using an affinity-purified polyclonal antibody for boar acrosin localized the protease at the acrosome region. Moreover, initiation of sperm motility was inhibited after activation in the presence of inhibitors for both trypsin-like and chymotrypsin-like proteases, while the effects of protease inhibitors on sperm velocity were uncertain. Our results indicate similarities in physiology and biochemistry of acrosome between sturgeon and mammals and suggest potential role of protease in the initiation of sperm motility in sturgeon.

In-depth proteomic analysis of carp (Cyprinus carpio L) spermatozoa

Using a combination of protein fractionation by one-dimensional gel electrophoresis and high performance liquid chromatography-electrospray ionization tandem mass spectrometry, we identified 348 proteins in carp spermatozoa, most of which were for the first time identified in fish. Dynein, tubulin, HSP90, HSP70, HSP60, adenosylhomocysteinase, NKEF-B, brain type creatine kinase, mitochondrial ATP synthase, and valosin containing enzyme represent high abundance proteins in carp spermatozoa. These proteins are functionally related to sperm motility and energy production as well as the protection of sperm against oxidative injury and stress. Moreover, carp spermatozoa are equipped with functionally diverse proteins involved in signal transduction, transcription, translation, protein turnover and transport. About 15% of proteins from carp spermatozoa identified here were also detected in seminal plasma which may be a result of leakage from spermatozoa into seminal plasma, adsorption of seminal plasma proteins on spermatozoa surface, and expression in both spermatozoa and cells secreting seminal plasma proteins. The availability of a catalog of carp sperm proteins provides substantial advances for an understanding of sperm function and for future development of molecular diagnostic tests of carp sperm quality, the evaluation of which is currently limited to certain parameters such as sperm count, morphology and motility or viability. The mass spectrometry data are available at ProteomeXchange with the dataset identifier PXD000877 (DOI: http://dx.doi.org/10.6019/PXD000877).

Effect of postthaw storage time and sperm-to-egg ratio on fertility of cryopreserved brook trout sperm

The aim of this study was to test the influence of postthaw storage time on sperm motility parameters of brook trout (n = 9). Furthermore, we examined the effect of sperm-to-egg ratios of 300,000:1 and 600,000:1 on fertility of postthaw, cryopreserved, brook trout sperm. The application of a cryopreservation procedure produced very high postthaw sperm motility (56.8 ± 4.0%). The cryopreserved sperm of brook trout could be stored up to 60 minutes without loss of the percentage of sperm motility (52.0 ± 9.0%). The fertilization capacity of brook trout postthaw sperm was comparable with the fertilization rate of fresh semen at a sperm-to-egg ratio as low as 300,000:1 (42.4 ± 14.0% and 36.5 ± 11.0% for eyed and hatched stages, respectively). The possibility of postthaw semen storage for the prolonged time and the obtainment of high fertilization rate at low sperm-to-egg ratio can lead to the significant improvement of brook trout semen cryopreservation procedure.

Characterization of lake minnow Eupallasella percnurus semen in relation to sperm morphology, regulation of sperm motility and interpopulation diversity

Sperm morphology and regulation of sperm motility of lake minnow Eupallasella percnurus, an endangered cyprinid, were investigated. Milt characteristics from two isolated populations of E. percnurus were compared to characterize the interpopulation diversity. Electron microscopic studies revealed that E. percnurus spermatozoa comprise simple, uniflagellate, anacrosomal aquasperm with species-specific features as an eccentrically located implantation of nuclear fossa and eccentric insertion of flagellum. Sperm motility was significantly inhibited by relatively low ion concentrations (150, 150 and 8 mM for NaCl, KCl and CaCl2 , respectively). Sperm maintained a high motility rate over a wide pH range (5.5-10.5), which may reflect adaptation to a highly variable environment. The two E. percnurus populations were markedly different in milt volume, sperm concentration, seminal plasma pH, sperm motility and beat cross frequency, which may result from genetic differences and environmental conditions.

Isolation, characterisation and cDNA sequencing of a new form of parvalbumin from carp semen

Parvalbumins (Pv) are calcium-binding proteins present mainly in the muscle and nervous system where they act as a Ca2+ buffer. Our previous work demonstrated the presence of Pv-I in carp semen and indicated the presence of a second Pv (Pv-II). The purpose of the present work was to identify, purify and determine the full-length cDNA sequence of Pv-II from carp testis. Pv-II from seminal plasma was purified by ion-exchange chromatography (IEC) and preparative electrophoresis, while the Pv-II from spermatozoa was purified by IEC, gel filtration and preparative electrophoresis. The purified Pv-II was submitted to an analysis of molecular mass, isoelectric point (pI), amino-acid sequence and oligomerisation ability. The amino-acid sequence was used to construct primers and obtain the full-length cDNA sequence of seminal-specific Pv-II from carp testis. Analysis of the cDNA sequence indicated that carp-testis Pv-II was distinct from carp-muscle parvalbumins. Pv-II was distinct from Pv-I regarding sequence, molecular mass and pI. Both parvalbumins had the ability to form oligomers or to bind to other proteins. Carp seminal plasma had a protective effect against parvalbumin oligomerisation. Pv-II underwent post-translational modification such as n-acetylation and cysteinylation. The present study is the first to report the full-length cDNA sequence of parvalbumin from carp testis.